The present invention relates to a semiconductor device having columnar electrodes on re-wiring.
There is known a semiconductor device called CSP (Chip Size Package). When the semiconductor device is to be mounted on a circuit board, a mounting technique called “face down bonding” is employed. In the case of this type of semiconductor device, columnar electrodes for connection with the circuit board, etc. are provided on a semiconductor substrate or via an intermediate substrate (interposer). FIG. 7A is a cross-sectional view showing an example of this type of conventional semiconductor device, and FIG. 7B is a cross-sectional view taken along line 7B—7B in FIG. 7A in the state in which a protection film 5 and the elements provided thereon are removed. This semiconductor device includes a semiconductor substrate 1 which is, e.g. a silicon substrate.
The semiconductor substrate 1 has a rectangular shape, as shown in FIG. 7B. A central region defined by a dot-and-dash line in FIG. 7B serves as a circuit element formation region 2. Where the semiconductor device is an LSI for driving a liquid crystal display panel, an oscillation circuit, a regulator circuit, an LC driver circuit, etc., although not shown, are provided in the circuit element formation region 2. A plurality of connection pads 3 are provided on an upper surface of the semiconductor substrate 1 on the outside of the circuit element formation region 2. Each connection pad 3 is formed of one end portion of a wiring segment 3a extended from the circuit element formation region 2 of semiconductor device 1. Each connection pad 3 is connected to the LC driver circuit, etc. via the wiring segment 3a. 
An insulating film 4 formed of, e.g. a semiconductor oxide, and protection film 5 formed of, e.g. polyimide are successively provided on the upper surface of semiconductor substrate 1 excluding the central portion of each connection pad. Thus, the central portion of the connection pad 3 is exposed via an opening portion 6 defined by the protection film 5. A re-wiring segment 7 is provided so as to extend from the exposed upper surface of the connection pad 3 to an upper surface of the protection film 5 on the circuit element formation region 2. A distal end portion of the re-wiring segment 7 functions as an external connection pad portion 7a. A columnar electrode 8 is provided on an upper surface of the external connection pad portion 7a. A sealing film 9 made of, e.g. an epoxy resin is provided over the entire upper surface of the assembly excluding the columnar electrodes 8. Although not shown, solder bumps are provided on the columnar electrodes 8, and this semiconductor device is connected to a circuit board, etc. via the solder bumps.
In the above semiconductor device, the re-wiring segments 7 are provided on the protection film 5 in the circuit element formation region 2, as mentioned above. Various signals flow through the re-wiring segments 7 since the re-wiring segments 7 function as interconnection wiring between the external circuit board, etc., on the one hand, and the circuits provided within the circuit element formation region 2, on the other. It is thus necessary to prevent crosstalk between the re-wiring segments 7 and the oscillation circuit, etc. provided in the circuit element formation region 2. For this purpose, it is necessary in the prior art to dispose the re-wiring segments 7 so as not to overlap in plan the oscillation circuit, etc. Because of this, the re-wiring segments 7 cannot freely be arranged, and there are very serious limitations to the design thereof.